In the prior art, LP gas supply systems for motor homes, recreational vehicles, and other places have generally included the storage tank supplying gas at high pressures, a pressure regulator downstream from the storage tank which steps down and regulates the pressure at a usable level, and the appliances downstream from the pressure regulator. It is possible that the pressure regulator in such systems can fail, thus supplying LP gas to the appliances at storage tank pressures. It is evident, therefore, that the failure of the pressure regulator in LP gas systems, creates a very dangerous condition and that protection against pressure regulator failure is certainly desired in such systems.
High pressure safety valves have been developed in the past which are located between the pressure regulator and the appliances in an LP gas system. Generally speaking, the prior art high pressure safety valves have been satisfactory in many respects, but at the same time they have proved to be disadvantageous in many respects also. Generally speaking, the prior art devices are slow acting, expensive to manufacture and have not provided certain advantageous features. While most of the prior art high pressure safety valves have been manually resettable, many of them allow the person resetting them to open the safety valve, even if the high pressure condition still exists. In addition, the prior art devices allow the high pressure to remain at the outlet of the safety valve, even after the valve has closed. Thus, while the prior art devices have prevented the flow of LP gas after the safety valve has closed, it is possible for a high pressure condition to remain at the input to the appliances.